/*
 * ice4j, the OpenSource Java Solution for NAT and Firewall Traversal.
 *
 * Copyright @ 2015 Atlassian Pty Ltd
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.ice4j.attribute;

import java.util.*;

import org.ice4j.*;

/**
 * This class is used for representing attributes not explicitly supported by
 * the stack. Such attributes will generally be kept in binary form and won't be
 * subdued to any processing by the stack. One could use this class for both
 * dealing with attributes in received messages, and generating messages
 * containing attributes not explicitly supported by the stack.
 *
 * @author Emil Ivov
 */
public class OptionalAttribute extends Attribute {
	byte[] attributeValue = null;

	protected OptionalAttribute(char attributeType) {
		super(attributeType);
	}

	/**
	 * Sets this attribute's fields according to attributeValue array.
	 *
	 * @param attributeValue
	 *            a binary array containing this attribute's field values and
	 *            NOT containing the attribute header.
	 * @param offset
	 *            the position where attribute values begin (most often offset
	 *            is equal to the index of the first byte after length)
	 * @param length
	 *            the length of the binary array.
	 * @throws StunException
	 *             if attrubteValue contains invalid data.
	 */
	void decodeAttributeBody(byte[] attributeValue, char offset, char length) throws StunException {
		this.attributeValue = new byte[length];
		System.arraycopy(attributeValue, offset, this.attributeValue, 0, length);
	}

	/**
	 * Returns a binary representation of this attribute.
	 *
	 * @return a binary representation of this attribute.
	 */
	public byte[] encode() {
		char type = getAttributeType();

		byte binValue[] = new byte[HEADER_LENGTH + attributeValue.length];

		// Type
		binValue[0] = (byte) (type >> 8);
		binValue[1] = (byte) (type & 0x00FF);
		// Length
		binValue[2] = (byte) (getDataLength() >> 8);
		binValue[3] = (byte) (getDataLength() & 0x00FF);

		System.arraycopy(attributeValue, 0, binValue, HEADER_LENGTH, attributeValue.length);

		return binValue;
	}

	/**
	 * Returns the length of this attribute's body.
	 *
	 * @return the length of this attribute's value.
	 */
	public char getDataLength() {
		return (char) attributeValue.length;
	}

	/**
	 * Returns the human readable name of this attribute.
	 *
	 * @return this attribute's name.
	 */
	public String getName() {
		return "Unknown Attribute";
	}

	/**
	 * Returns a reference to the unparsed body of this attribute.
	 *
	 * @return a reference to this attribute's unparsed value.
	 */
	public byte[] getBody() {
		return attributeValue;
	}

	/**
	 * Copies the speicified byte array segment as the body of this attribute.
	 *
	 * @param body
	 *            the body to copy
	 * @param offset
	 *            the position to start
	 * @param length
	 *            the length to copy
	 */
	public void setBody(byte[] body, int offset, int length) {
		this.attributeValue = new byte[length];
		System.arraycopy(body, offset, this.attributeValue, 0, length);
	}

	/**
	 * Compares two STUN Attributes. Two attributes are considered equal when
	 * they have the same type length and value.
	 *
	 * @param obj
	 *            the object to compare this attribute with.
	 * @return true if the attributes are equal and false otherwise.
	 */
	public boolean equals(Object obj) {
		if (!(obj instanceof OptionalAttribute))
			return false;

		return (obj == this || Arrays.equals(((OptionalAttribute) obj).attributeValue, attributeValue));
	}
}
